Thermodynamics

Introduction

So today we are going to learn about some hot stuff!! I hope you were not a hoping for me to talk about models!! Why would I wan't to talk about 3D models and filament. That would just be gross!! :-( No, what we are going to learn about is Thermodynamics!! I know its a long word!! You are probably going to turn off the screen now because you are scared of big words, don't worry. Thermodynamics is PRETTY cool!! So listen up!!

What is Thermodynamics

You are probably so confused right now!! You read this BIG word and you are like "Avery, it says thermo, so we should be talking about heat, right? But then it says dynamics!! But isn't that physics?" Yes, and yes!! Thermodynamics is a apart of physics that deals with the relationship between heat and energy. Yeah, I know, adults and there big words and science stuff!! Pretty much it means I will be describing how heat is converted to other energy and how it affects matter!! Still a little fuzzy? Keep on reading!!

Heat is a form of energy, so it can not be destroyed, only converted.

Temperature!!

The amount of heat transferred by a substance depends on the speed and number of atoms or molecules in motion, so the faster the atoms or molecules move, the higher the temperature. And the more atoms or molecules that are in motion, the greater the quantity of heat they transfer. So if the atoms and molecules where sloths it would be cooler than a bunch of cheetah atoms and molecules.

Temperature which you can probably tell from my comparison is the measure of the average movement (kinetic energy) of the particles in a little bit of the matter. It is measured by degrees on a standard scale. Usually they use Celsius instead of Fahrenheitm but they are both used.

Most scientists use a scale which you probably haven't heard of before, it is called Kelvin. They use K because it works in calculations. The scale uses the same increment as celsi.... Wait what is increment? Increment is a "increase or addition, especially one of a series on a fixed scale". Okay now I can continue. The scale uses the same increment as Celsius. BUT K starts at absolute zero, which means there is nothing moving, at all!!

Specific heat

Okay, let's make this quick and easy!! Specific heat is the exact heat it takes to increase the temperature of a certain matter. But it is differnt for every matter. It depends on the number of atoms.

Thermal conductivity

Thermal conductivity is the rate at which heat passes through a specified material. It is expressed as the amount of heat that flows per unit time through a unit area with a temperature gradient of one degree per unit distance. 😰 I know that is hard to understand, really this is all it means. The way the measurement is being told is , howmuch heat, flows at this speed, through this much space.

Some things with high conductivity are used in certain jobs while others that are thermal resistant are used.

Newtons law of cooling

In 1701, Sir Issac Newton first started his law of cooling in a short article in a Philosophical Transactions of the Royal Society, called

Sir Issac Newtons title-Scala graduum Caloris

Adult title-A Scale of the Degrees of heat

Kid title - A thermometer

In his article he talk in a forgotten language, so simply what he talked about is this.

"The rate of change of temperature is proportional to the difference between the temperature of the object and that of the surrounding environment".

This result in an exponential decay in temperature difference. For example, if a warm object is placed in a cold tub of water, for a certain amount of time, the difference in their temperatures will decrease by half. The same exact numbers would appear if you did it again. It will continue by decreasing by halves intill it is to small to measure.

Heat transfer

Heat is transfered from different matters all the time, in three different ways.

1. Conduction- the transfer through solid material or between bodies (direct contact)

The Carnot cycle

In 1824, Nicholas Léonard Sadi Carnot proposed a model for a heat engine based on what has come to be known as the Carnot cycle. The cycle explains the relationships among pressure, volume and temperature of gasses and how an input of energy can change form and do work outside the system.

Compressing a gas makes it increase in temperature, heat can be removed my a heat exchanger. That allows it to expand and causes it to cool down.

Hearing a gas increases it's pressure, causing it to expand. The expansive pressure can be used to drive a piston, making the heat energy to kinetic energy. Thats how a heat engine works.

Entropy

All thermodynamics systems generate and waste heat, just like making a cake, you make the cake, but you have garbage. Entropy in any closed system always increases, never ever decreases. Additionally, moving parts produce waste heat due to friction,and radiative heat will leak from the system, it is unavoidable!!